Radio-frequency lighting control system with occupancy sensing

ABSTRACT

A load control system controls an electrical load provided in a space and comprises a load control device and one or more occupancy sensors. The load control device controls the load in response to the wireless control signals received from the occupancy sensors. Each occupancy sensor transmits an occupied control signal to the load control device in response to detecting an occupancy condition in the space and a vacant control signal to the load control device in response to detecting a vacancy condition. The load control device turns on the load in response to receiving the occupied control signal from at least one of the occupancy sensors, and turns off the load in response to receiving vacant control signals from both of the occupancy sensors. The load control device is operable to determine that no wireless control signals have been received from the occupancy sensors for the length of a predetermined timeout period and to subsequently turn off the load.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/163,889, filed Jun. 20, 2011 in the name of James P. Steiner, AndrewPeter Schmalz, Andrew Ryan Offenbacher, Adam Schrems and Brian RaymondValenta which is a continuation of U.S. patent application Ser. No.12/203,518, filed Sep. 3, 2008, now U.S. Pat. No. 8,009,042, issued Aug.30, 2011 entitled RADIO-FREQUENCY LIGHTING CONTROL SYSTEM WITH OCCUPANCYSENSING the entire contents of which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to occupancy and vacancy sensors fordetecting an occupancy or a vacancy in a space, and more particularly,to a wireless load control system including a plurality ofbattery-powered occupancy or vacancy sensors for detecting an occupancyor a vacancy in a space, and a load control device for controlling theamount of power delivered to an electrical load in response to theoccupancy or vacancy sensors.

Description of the Related Art

Occupancy and vacancy sensors are often used to detect occupancy and/orvacancy conditions in a space in order to control an electrical load,such as, for example, a lighting load. An occupancy sensor typicallyoperates to turn on the lighting load when the occupancy sensor detectsthe presence of a user in the space (i.e., an occupancy event) and thento turn off the lighting load when the occupancy sensor detects that theuser has left the space (i.e., a vacancy event). A vacancy sensor onlyoperates to turn off the lighting load when the vacancy sensor detects avacancy in the space. Therefore, when using a vacancy sensor, thelighting load must be turned on manually (e.g., in response to a manualactuation of a control actuator).

Occupancy and vacancy sensors have often been provided in wall-mountedload control devices that are coupled between an alternating-current(AC) power source and an electrical load for control of the amount ofpower delivered to the electrical load. Such wall-mounted load controldevices typically comprise internal detectors, such as, for example, apyroelectric infrared (PIR) detector, and a lens for directing energy tothe PIR detector for detecting the presence of the user in the space.However, since the wall-mounted load control devices are mounted to awall in a standard electrical wallbox (i.e., replacing a standard lightswitch), the detection of energy by the PIR detector may be hindered dueto the direction that the load control device is facing and by obstaclesin the space, thus increasing the likelihood that the load controldevice may not detect the presence of a user.

Some prior art occupancy and vacancy sensors have been provided as partof lighting control systems. These sensors are typically coupled via awired control link to a lighting controller (e.g., a central processor),which then controls the lighting loads accordingly. Since the controllink is typically a low-voltage control link, these occupancy andvacancy sensors are not required to be mounted in electrical wallboxes,but may be mounted to the ceiling or high on a wall. Therefore, theoccupancy and vacancy sensors may be positioned optimally to detect thepresence of the user in all areas of the space. However, these prior artlighting control systems require advanced system components andconfiguration procedures in order to operate properly.

Thus, there is a need for a simple lighting control system that hasoccupancy or vacancy sensors which may be easily and optimally installedinto a space.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, a radio-frequencyload control system with occupancy sensing comprises a load controldevice and first and second battery-powered occupancy sensors. The loadcontrol device is connected between an AC power source and an electricalload, and contains a radio-frequency (RF) receiver circuit for receivingradio frequency signals. Each of the first and second battery-poweredoccupancy sensors are fixable to a surface of a room in which theelectrical load is located for transmitting an RF signal in response tothe presence of an occupant in the room. The second occupancy sensor isspaced from the location of the first occupancy sensor. Each occupancysensor comprises an enclosed plastic housing including at least onebattery, a detector for sensing the presence or absence of occupants inthe room, and a RF transmitter circuit for producing the RF signal whichis modulated to indicate the presence or absence of the occupant in theroom, the RF signals of the occupancy sensors having respectiveidentifying information to identify themselves to the load controldevice. The load control device receives the RF signals transmitted bythe occupancy sensors and controls the current supplied to theelectrical load in a predetermined dependence on the detection of anoccupancy or a vacancy in the room.

According to another embodiment of the present invention, a load controlsystem for controlling the amount of power delivered from an AC powersource to an electrical load provided in a space comprises two occupancysensors and a load control device operable to enable the delivery ofpower to the electrical load in response to receiving an occupiedwireless control signal from at least one of the occupancy sensors, andto cease the delivery of power to the electrical load in response toreceiving vacant control signals from both of the occupancy sensors. Theload control device is adapted to be coupled in series electricalconnection between the AC power source and the electrical load forcontrol of the amount of power delivered to the electrical load. Theload control device receives wireless control signals and controls theamount of power delivered to the electrical load in response to thewireless control signals. Each of the two occupancy sensorsindependently detects an occupancy condition in the space, transmits theoccupied wireless control signal to the load control device in responseto detecting the occupancy condition, and transmits the vacant wirelesscontrol signal to the load control device in response to detecting avacancy condition in the space.

In addition, a method of controlling the amount of power delivered froman AC power source to an electrical load provided in a space comprisesthe steps of: (1) providing two occupancy sensors in the space; (2)detecting by one of the occupancy sensors an occupancy condition in thespace; (3) transmitting by one of the occupancy sensors an occupiedwireless control signal in response to the step of detecting theoccupancy condition; (4) receiving the occupied wireless control signalfrom at least one of the occupancy sensors; (5) enabling the delivery ofpower to the electrical load in response to the step of receiving theoccupied wireless control signal from at least one of the occupancysensors; (6) detecting by one of the occupancy sensors a vacancycondition in the space; (7) transmitting by one of the occupancy sensorsa vacant wireless control signal in response to the step of detecting avacancy condition in the space; (8) receiving vacant control signalsfrom both of the occupancy sensors; and (9) ceasing the delivery ofpower to the electrical load in response to the step of receiving vacantcontrol signals from both of the occupancy sensors.

A sensor system for controlling a lighting load located within a room isalso described herein. The sensor system comprises an RF-responsivelight control device for turning on and turning off the lighting load,and at least first and second spaced occupancy sensors disposed tomonitor occupancy in different areas of the room. Each of the first andsecond sensors produce first and second respective occupied and vacantRF signals to the light control device in response to the sensing of arespective presence or absence of an occupant in the room. The lightcontrol device turns on the lighting load in response to receiving anoccupied RF signal from either of the first or second sensors, and turnsoff the lighting load in response to receiving an vacant RF signal fromboth of the sensors.

Further, a process of controlling a lighting load in a room dependentupon the occupancy or vacancy of the room comprises the steps of: (1)providing first and second spaced occupancy sensors mounted within theroom; (2) monitoring by the first and second occupancy sensors for thepresence of one or more persons in the room; (3) transmitting by thefirst and second occupancy sensors respective RF signals includingoccupancy or vacancy information with an identifier of the respectivesensor producing such information; (4) receiving the RF signals by aload control device; (5) turning on by the load control device thelighting load in response to receiving an occupied RF output signal fromeither the first or the second sensor; and (6) turning off by the loadcontrol device the lighting load in response to receiving vacant RFsignals from both of the first and second sensors.

According to another embodiment of the present invention, a load controlsystem for controlling the amount of power delivered from an AC powersource to an electrical load provided in a space comprises an occupancysensor and a load control device operable to determine that no wirelesscontrol signals have been received from the occupancy sensor for thelength of a predetermined timeout period and to subsequently cease thedelivery of power to the electrical load. The load control devicereceives the wireless control signals and controls the amount of powerdelivered to the electrical load in response to the wireless controlsignals. The occupancy sensor detects an occupancy condition in thespace and transmits a first wireless control signal to the load controldevice in response to detecting the occupancy condition, and transmits asecond wireless control signal to the load control device in response todetecting a continued occupancy condition in the space. The load controldevice enables the delivery of power to the electrical load in responseto the first wireless control signal, determines that no wirelesscontrol signals have been received from the occupancy sensor for thelength of the predetermined timeout period, and subsequently ceases thedelivery of power to the electrical load.

In addition, a method of controlling the amount of power delivered froman AC power source to an electrical load provided in a space comprisesthe steps of: (1) providing an occupancy sensor in the space; (2)detecting by the occupancy sensor an occupancy condition in the space;(3) transmitting by the occupancy sensor a first wireless control signalin response to the step of detecting the occupancy condition; (4)enabling the delivery of power to the electrical load in response to thefirst wireless control signal; (5) detecting by the occupancy sensor acontinued occupancy condition in the space; (6) transmitting by theoccupancy sensor a second wireless control signal in response to thestep of detecting a continued occupancy condition in the space; (7)determining that no wireless control signals have been received from theoccupancy sensor for the length of a predetermined timeout period; and(8) ceasing the delivery of power to the electrical load in response tothe step of determining that no wireless control signals have beenreceived.

According to another embodiment of the present invention, a load controlsystem for controlling the amount of power delivered from an AC powersource to an electrical load provided in a space comprises a loadcontrol device an occupancy sensor comprising an occupancy detector fordetecting an occupancy condition in the space and an ambient light leveldetector for measuring the ambient light level in the space. The loadcontrol device receives wireless control signals and controls the amountof power delivered to the electrical load in response to the wirelesscontrol signals. The occupancy sensor compares the ambient light levelto an ambient light level threshold, transmits a first predeterminedwireless control signal to the load control device in response todetermining that the ambient light level is less than the threshold, andtransmits a second predetermined wireless control signal to in responseto determining that the ambient light level is greater than thethreshold.

In addition, a wall or ceiling mounted occupancy sensor comprises: (1)at least one battery; (2) a controller coupled to the battery; (3) a PIRoccupancy detector for sensing the presence or absence of an occupant ina room, the occupancy detector circuit coupled to the controller anddelivering occupancy or vacancy information to the controller; (4) an RFtransmitter coupled to the battery and the controller for transmittingan RF signal containing information related to the presence or absenceof an occupant in the room; (5) an ambient light detector coupled to thecontroller, the controller compares the level of ambient light withinthe area to an ambient light threshold, whereby the RF signaltransmitted by the RF transmitter is modified in accordance with thecomparison of the level of ambient light within the area and the ambientlight threshold; and (6) an enclosure housing containing the battery,the controller, and the PIR detector, the RF transmitter, and theambient light detector, the housing having mounting structure formounting the sensor to a wall or ceiling surface of a room.

According to another embodiment of the present invention, a load controlsystem for controlling the amount of power delivered from an AC powersource to an electrical load provided in a space comprises an occupancysensor and a load control device operable to store operatingcharacteristics of the load control system. The load control devicereceives wireless control signals and controls the amount of powerdelivered to the electrical load in response to the wireless controlsignals. The occupancy sensor comprises an occupancy detector circuitfor generating an occupancy control signal representative of anoccupancy condition in the space, a controller responsive to theoccupancy control signal, and a wireless transmitter for transmittingthe wireless control signals. The controller determines whether theoccupancy condition is presently occurring in the space based upon eachof a plurality of occupancy criteria and generates a result for each ofthe determinations of the occupancy condition at each of the pluralityof occupancy criteria. The occupancy sensor transmits to the loadcontrol device each of the results of the determinations of theoccupancy condition at each of the plurality of occupancy criteria. Theload control device is characterized by a predetermined one of theplurality of occupancy criteria, and selects one of the results of eachof the determinations of the occupancy condition at each of theplurality of occupancy criteria based upon the predetermined one of theplurality of occupancy criteria. The load control device controls theamount of power delivered to the electrical load in response to theselected results of the determination of the occupancy condition.

Further, a method of controlling the amount of power delivered from anAC power source to an electrical load provided in a space comprises thesteps of: (1) generating an occupancy control signal representative ofan occupancy condition in the space; (2) determining whether theoccupancy condition is presently occurring in the space based upon eachof a plurality of occupancy criteria; (3) generating a result for eachof the determinations of the occupancy condition at each of theplurality of occupancy criteria; (4) transmitting each of the results ofthe determinations of the occupancy condition at each of the pluralityof occupancy criteria; (5) selecting one of the results of each of thedeterminations of the occupancy condition at each of the plurality ofoccupancy criteria based upon a predetermined one of the plurality ofoccupancy criteria; and (6) controlling the amount of power delivered tothe electrical load in response to the step of selecting one of theresults.

Other features and advantages of the present invention will becomeapparent from the following description of the invention that refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simple diagram of a radio-frequency (RF) lighting controlsystem having a dimmer switch and remote occupancy sensors for controlof the amount of power delivered to a lighting load according to a firstembodiment of the present invention;

FIG. 1B is a simplified state diagram illustrating the operation of oneof the occupancy sensors of the RF lighting control system of FIG. 1A;

FIG. 1C is a simplified state diagram illustrating the state of afailsafe timer of the dimmer switch of the RF lighting control system ofFIG. 1A;

FIG. 1D is a simplified state diagram illustrating how the dimmer switchof the RF lighting control system of FIG. 1A controls the lighting load;

FIG. 2A is a simplified block diagram of the dimmer switch of the RFlighting control system of FIG. 1A;

FIG. 2B is a simplified block diagram of one of the remote occupancysensors of the RF lighting control system of FIG. 1A;

FIG. 3 is a simplified circuit diagram of an occupancy detector circuitof the occupancy sensor of FIG. 2B;

FIG. 4A is a front exploded perspective view of the occupancy sensor ofFIG. 2B;

FIG. 4B is a rear exploded perspective view of the occupancy sensor ofFIG. 2B;

FIG. 4C is a perspective view of a multi-functional structure of theoccupancy sensor of FIG. 2B;

FIG. 4D is a rear perspective view of a base portion of the occupancysensor of FIG. 2B with batteries removed;

FIG. 5 is a flowchart of a rear actuator procedure executed by acontroller of the occupancy sensor of FIG. 2B when an actuator on a rearsurface of the base portion of FIG. 4D is pressed;

FIGS. 6A and 6B is a simplified flowchart of a dimmer actuator procedureexecuted by a controller of the dimmer switch of FIG. 2A;

FIG. 7 is a simplified flowchart of an assignment procedure executed bythe controller of the dimmer switch of FIG. 2A;

FIG. 8 is a flowchart of an occupancy detection procedure executedperiodically by the controller of the occupancy sensor of FIG. 2Baccording to the first embodiment of the present invention;

FIG. 9 is a flowchart of a transmission timer procedure executed by thecontroller of the occupancy sensor of FIG. 2B according to the firstembodiment of the present invention;

FIG. 10 is a flowchart of an occupancy timer procedure executed by thecontroller of the occupancy sensor of FIG. 2B according to the firstembodiment of the present invention;

FIG. 11 is a flowchart of a received message procedure executed by thecontroller of the dimmer switch of FIG. 2A according to the firstembodiment of the present invention;

FIG. 12 is a simplified flowchart of a failsafe timer procedure executedby the controller according to the first embodiment of the presentinvention;

FIG. 13 is a flowchart of an occupancy detection procedure executedperiodically by the controller of the occupancy sensor of FIG. 2Baccording to a second embodiment of the present invention;

FIG. 14 is a flowchart of a transmission procedure executed by thecontroller of the occupancy sensor of FIG. 2B according to the secondembodiment of the present invention;

FIG. 15 is a flowchart of a received message procedure executed by thecontroller of the dimmer switch of FIG. 2A according to the secondembodiment of the present invention;

FIG. 16 is a flowchart of an occupancy timer procedure executed by thecontroller of the dimmer switch of FIG. 2A according to the secondembodiment of the present invention;

FIG. 17A is a simplified block diagram of a lighting control systemhaving a dimmer switch, remote occupancy sensors, and a remote controlfor controlling the amount of power delivered to a lighting loadaccording to a third embodiment of the present invention;

FIG. 17B is a simplified state diagram illustrating how the dimmerswitch of the RF lighting control system of FIG. 17A controls thelighting load;

FIG. 17C is a simplified state diagram illustrating the state of afailsafe timer of one of the occupancy sensors of the RF lightingcontrol system of FIG. 17A; and

FIG. 18 is a simplified schematic diagram of an occupancy detectorcircuit 232′ according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing summary, as well as the following detailed description ofthe preferred embodiments, is better understood when read in conjunctionwith the appended drawings. For the purposes of illustrating theinvention, there is shown in the drawings an embodiment that ispresently preferred, in which like numerals represent similar partsthroughout the several views of the drawings, it being understood,however, that the invention is not limited to the specific methods andinstrumentalities disclosed.

FIG. 1A is a simple diagram of a radio-frequency (RF) lighting controlsystem 100 comprising a dimmer switch 110 and two remote occupancysensors 120 (e.g., passive infrared sensors). The dimmer switch 110 isadapted to be coupled in series electrical connection between an ACpower source 102 and a lighting load 104 for controlling the amount ofpower delivered to the lighting load. The dimmer switch 110 may beadapted to be wall-mounted in a standard electrical wallbox.Alternatively, the dimmer switch 110 could be implemented as a table-topload control device. The dimmer switch 110 comprises a faceplate 112 anda bezel 113 received in an opening of the faceplate. The dimmer switch110 further comprises a toggle actuator 114, i.e., a button, and anintensity adjustment actuator 116. Actuations of the toggle actuator 114toggle, i.e., turn off and on, the lighting load 104. Actuations of anupper portion 116A or a lower portion 116B of the intensity adjustmentactuator 116 respectively increase or decrease the amount of powerdelivered to the lighting load 104 and thus increase or decrease theintensity of the lighting load 104 from a minimum intensity (e.g., 1%)to a maximum intensity (e.g., 100%). A plurality of visual indicators118, e.g., light-emitting diodes (LEDs), are arranged in a linear arrayon the left side of the bezel 113. The visual indicators 118 areilluminated to provide feedback of the intensity of the lighting load104. An example of a dimmer switch having a toggle actuator 114 and anintensity adjustment actuator 116 is described in greater detail in U.S.Pat. No. 5,248,919, issued Sep. 29, 1993, entitled LIGHTING CONTROLDEVICE, the entire disclosure of which is hereby incorporated byreference.

The remote occupancy sensors 120 are removably mountable to a ceiling ora wall, for example, in the vicinity of (i.e., a space around) thelighting load 104 controlled by the dimmer switch 110, and are operableto detect occupancy conditions in the vicinity of the lighting load. Theoccupancy sensors 120 may be spaced apart to detect occupancy conditionsin different areas of the vicinity of the lighting load 104. The remoteoccupancy sensors 120 each include an internal detector, e.g., apyroelectric infrared (PIR) detector 310 (FIG. 3), which is housed in anenclosure 122 (e.g., an enclosed plastic housing) and will be describedin greater detail below. The enclosure 122 comprises a lens 124 (e.g.,an outwardly domed lens) provided in a front surface 125 of theenclosure 122 (which defines a top plate of the occupancy sensor 120).The internal detector is operable to receive infrared energy from anoccupant in the space via the lens 124 to thus sense the occupancycondition in the space. The occupancy sensors 120 are operable toprocess the output of the PIR detector 310 to determine whether anoccupancy condition (i.e., the presence of the occupant) or a vacancycondition (i.e., the absence of the occupant) is presently occurring inthe space, for example, by comparing the output of the PIR detector 310to a predetermined occupancy voltage threshold. Alternatively, theinternal detector could comprise an ultrasonic detector, a microwavedetector, or any combination of PIR detectors, ultrasonic detectors, andmicrowave detectors.

FIG. 1B is a simplified state diagram illustrating the operation of theoccupancy sensors 120 of the RF lighting control system 100. Theoccupancy sensors 120 each operate in an “occupied” state or a “vacant”state in response to the detections of occupancy or vacancy conditions,respectively, in the space. If one of the occupancy sensors 120 is inthe vacant state and the occupancy sensor determines that the space isoccupied in response to the PIR detector 310, the occupancy sensorchanges to the occupied state.

During a setup procedure of the RF lighting control system 100, thedimmer switch 110 may be assigned to (i.e., associated with) one or moreremote occupancy sensors 120. The remote occupancy sensors 120 transmitdigital messages wirelessly via RF signals 106 to the dimmer switch 110in response to the present state of the occupancy sensors. A messagetransmitted by the remote occupancy sensors 120 may include a commandand identifying information, for example, a 52-bit serial number (i.e.,a unique identifier) associated with the transmitting occupancy sensor.The dimmer switch 110 is responsive to messages containing the serialnumbers of the remote occupancy sensors 120 to which the dimmer switchis assigned.

The commands included in the digital messages transmitted by theoccupancy sensors 120 may comprise an occupied command (e.g., anoccupied-take-action command or an occupied-no-action command) or avacant command. When the lighting load 104 is off, the dimmer switch 110is operable to turn on the lighting load in response to receiving afirst occupied-take-action command from any one of the occupancy sensors120. The dimmer switch 110 is operable to turn off the lighting load 104in response to the last vacant command received from those occupancysensors 120 from which the occupancy sensor received eitheroccupied-take-action or occupied-no-action commands. For example, if theoccupancy sensors 120 both transmit occupied-take-action commands to thedimmer switch 110, the dimmer switch will not turn off the lighting load104 until subsequent vacant commands are received from both of theoccupancy sensors.

Each occupancy sensor 120 also comprises an ambient light detector 234(FIG. 2B), e.g., a photocell, for detecting the level of ambient lightaround the occupancy sensor. The occupancy sensor 120 only measures theambient light level when an occupancy condition is first detected. Theambient light level is compared to a predetermined ambient light levelthreshold. If the measured ambient light level is less than thepredetermined level when an occupancy condition is first detected by oneof the occupancy sensors 120, the occupancy sensor transmits theoccupied-take-action command to the dimmer switch 110. On the otherhand, if the measured ambient light level is greater than thepredetermined level when an occupancy condition is first detected, theoccupancy sensor 120 transmits the occupied-no-action command to thedimmer switch 110. Accordingly, the dimmer switch 110 does not turn onthe lighting load 104 if the ambient light level in the space issufficiently high.

While one of the occupancy sensors 120 continues to detect the occupancycondition in the space (i.e., a continued occupancy condition), theoccupancy sensor regularly transmits the occupied-no-action command tothe dimmer switch 110, such that the dimmer switch knows that theoccupancy sensor 120 is still in the occupied state. In response toreceiving the occupied-no-action command, the dimmer switch 110 eithermaintains the lighting load 104 on (e.g., if an occupied-take-actioncommand was previously received) or maintains the lighting load off.

The occupancy sensors 120 are each characterized by a predeterminedoccupancy sensor timeout period T_(TIMEOUT), which provides some delayin the adjustment of the state of the occupancy sensor, specifically, inthe transition from the occupied state to the vacant state. Thepredetermined occupancy sensor timeout period T_(TIMEOUT) may beuser-selectable ranging, for example, from five to thirty minutes. Eachoccupancy sensor 120 will not transmit a vacant command until theoccupancy sensor timeout period T_(TIMEOUT) has expired. Each occupancysensor 120 maintain an occupancy timer to keep track of the time thathas expired since the last detected occupancy condition. The occupancysensors 120 periodically restart the occupancy timers in response todetermining an occupancy condition (as shown by “Restart Timer” in thestate diagram of FIG. 1B). Accordingly, the occupancy sensors 120 do notchange to the vacant state, and the lighting load 104 is not turned off,in response to brief periods of a lack of movement of the occupant inthe space. If the occupancy sensor 120 fails to continue detecting theoccupancy conditions, the occupancy sensor 120 waits for the length ofthe occupancy sensor timeout period T_(TIMEOUT) (as shown by “Wait” inthe state diagram of FIG. 1B). After the occupancy timer expires, theoccupancy sensor 120 changes to the vacant state and transmits a vacantcommand to the dimmer switch 110 (as shown by “Timeout” in the statediagram of FIG. 1B).

If the dimmer switch 110 does not receive a digital message from any ofthe occupancy sensors 120 for a failsafe timeout period T_(FAILSAFE),the dimmer switch 110 assumes that all of the occupancy sensors are inthe vacant state and turns off the lighting load 104. To accomplish thiscontrol, the dimmer switch 110 maintains a failsafe timer. FIG. 1C is asimplified state diagram illustrating the state of the failsafe timer ofthe dimmer switch 110. The failsafe timer is started when the lightingload 104 is controlled from off to one and at least one occupancy sensor120 is assigned to the dimmer switch 110. If there are not any occupancysensors 120 assigned to the dimmer switch 110 when the lighting load 104is turned on, the failsafe timer is not started. The failsafe timer isreset to the value of the failsafe timeout period T_(FAILSAFE) inresponse to receiving a digital message from any of the occupancysensors 120 assigned to the dimmer switch 110 or in response toactuations of any the dimmer actuators (which do not cause the lightingload 104 to be turned off). When the failsafe timer expires, the dimmerswitch 110 assumes that all of the occupancy sensors are in the vacantstate and turns off the lighting load 104. The failsafe timer is stoppedwhenever the lighting load 104 is turned off (i.e., when vacant commandsare received from all occupancy sensors 120, when one of the dimmeractuators is actuated to turn off the lighting load, or when thefailsafe timer expires).

The dimmer switch 110 controls the lighting load 104 in response to thereceived digital messages as well as actuations of the dimmer actuators(i.e., toggle actuator 114 and the intensity adjustment actuator 116)and the failsafe timer. FIG. 1D is a simplified state diagramillustrating how the dimmer switch 110 controls the state of thelighting load 104 (i.e., between on and off). The dimmer switch 110 doesnot control the intensity of the lighting load 104 in response to theoccupied-no-action commands. The dimmer switch 110 turns on the lightingload 104 when the first occupied-take-action command is received or whenone of the dimmer actuators is actuated to turn on the lighting load.Further, the dimmer switch 110 turns off the lighting load 104 when thelast vacant command is received from the occupancy sensors 120, when oneof the dimmer actuators is actuated to turn off the lighting load, orwhen the failsafe timer expires.

FIG. 2A is a simplified block diagram of the dimmer switch 110. Thedimmer switch 110 comprises a controllably conductive device 210 coupledin series electrical connection between the AC power source 102 and thelighting load 104 for control of the power delivered to the lightingload. The controllably conductive device 210 may comprise any suitabletype of bidirectional semiconductor switch, such as, for example, atriac, a field-effect transistor (FET) in a rectifier bridge, or twoFETs in anti-series connection. The controllably conductive device 210includes a control input coupled to a drive circuit 212. The input tothe control input will render the controllably conductive device 210conductive or non-conductive, which in turn controls the power suppliedto the lighting load 104.

The drive circuit 212 provides control inputs to the controllablyconductive device 210 in response to command signals from a controller214. The controller 214 is preferably implemented as a microcontroller,but may be any suitable processing device, such as a programmable logicdevice (PLD), a microprocessor, or an application specific integratedcircuit (ASIC). The controller 214 receives inputs from the toggleactuator 114 and the intensity adjustment actuator 116 and controls thestatus indicators 118. The controller 214 is also coupled to a memory216 for storage of the preset intensity of lighting load 104 and theserial number of the occupancy sensor 120 to which the dimmer switch 110is assigned. The memory 216 may be implemented as an external integratedcircuit (IC) or as an internal circuit of the controller 214. A powersupply 218 generates a direct-current (DC) voltage V_(CC) for poweringthe controller 214, the memory 216, and other low-voltage circuitry ofthe dimmer switch 110.

A zero-crossing detector 220 determines the zero-crossings of the inputAC waveform from the AC power supply 102. A zero-crossing is defined asthe time at which the AC supply voltage transitions from positive tonegative polarity, or from negative to positive polarity, at thebeginning of each half-cycle. The zero-crossing information is providedas an input to controller 214. The controller 214 provides the controlinputs to the drive circuit 212 to operate the controllably conductivedevice 210 (i.e., to provide voltage from the AC power supply 102 to thelighting load 104) at predetermined times relative to the zero-crossingpoints of the AC waveform.

The dimmer switch 110 further comprises an RF receiver 222 and anantenna 224 for receiving the RF signals 106 from the occupancy sensor120. The controller 214 is operable to control the controllablyconductive device 210 in response to the messages received via the RFsignals 106. Examples of the antenna 224 for wall-mounted dimmerswitches, such as the dimmer switch 110, are described in greater detailin U.S. Pat. No. 5,982,103, issued Nov. 9, 1999, and U.S. patentapplication Ser. No. 10/873,033, filed Jun. 21, 2006, both entitledCOMPACT RADIO FREQUENCY TRANSMITTING AND RECEIVING ANTENNA AND CONTROLDEVICE EMPLOYING SAME. The entire disclosures of both are herebyincorporated by reference.

FIG. 2B is a simplified block diagram of one of the remote occupancysensors 120. The remote occupancy sensor 120 comprises a controller 230and an occupancy detector circuit 232, which provides the controllerwith an occupancy control signal V_(OCC) representative of whether thespace is occupied or not. The controller 230 receives an ambient lightlevel control signal V_(AMB) representative of the level of ambientlight around the occupancy sensor from the ambient light detector 234. Aplurality of actuators 236 provide user inputs to the occupancy sensor120 for use during configuration and installation of the lightingcontrol system 100 as will be described in greater detail below. Thecontroller 230 is operable to illuminate a plurality of visualindicators 238, e.g., light-emitting diodes (LEDs), to provide feedbackto the user during configuration and installation of the occupancysensor 120.

According to a first embodiment of the present invention, the occupancysensors 120 are each operable to store in a memory 240 the values of thevarious operating characteristics of the lighting control system 100,e.g., the occupancy voltage threshold, the ambient light levelthreshold, and the occupancy sensor timeout period T_(TIMEOUT). Thememory 240 may be implemented as an external integrated circuit (IC) oras an internal circuit of the controller 230. To adjust the values ofthe operating characteristics, the user must access the occupancy sensor120 to actuate the actuators 236. The occupancy sensors 120 use theoperating characteristics to change between the occupied state and thevacant state as will be described in greater detail below. The occupancysensors 120 also store the serial number in the memory 240. The serialnumber may be programmed into the memory 240, for example, duringmanufacture of the occupancy sensor 120.

The remote occupancy sensor 120 further comprises an RF transmitter 242coupled to the controller 230 and an antenna 244. In response todetermining an occupancy or a vacancy condition of the space, thecontroller 230 causes the RF transmitter 242 to transmit a digitalmessage to the dimmer switch 110 via the RF signals 106. Eachtransmitted message comprises the serial number of the remote occupancysensor 120 and the appropriate command dependent upon the variousoperating characteristics of the occupancy sensor and the magnitudes ofthe occupancy control signal V_(OCC) and the ambient light level controlsignal V_(AMB). Alternatively, the RF transmitter 242 of the occupancysensors 120 and the RF receiver 222 of the dimmer switch 110 could bothcomprise RF transceivers to allow for two-way communication between theoccupancy sensors and the dimmer switch.

The occupancy sensor 120 also comprises two batteries: a first batteryV1 and a second battery V2. The first battery V1 provides a firstbattery voltage V_(CC1) referenced to a first circuit common, and thesecond battery V2 provides a second battery voltage V_(CC2) referencedto a second circuit common. For example, the magnitudes of the first andsecond battery voltages V_(CC1), V_(CC2) may be the same, e.g.,approximately 3 volts. The second battery V2 powers only the occupancydetector circuit 232, while the first battery V1 powers the controller230, the RF transmitter 242, and the other circuitry of the occupancysensor 120. Since the occupancy detector circuit 232 is powered by aseparate battery from the other circuitry, the occupancy detectorcircuit is isolated from the noisy circuitry (e.g., the controller 230and the RF transmitter 242) of the occupancy sensor 120 withoutexcessive electronic filtering. Accordingly, the amount of noise presentin the occupancy detector circuit 232 is dramatically reduced withoutthe use of advanced filters.

The magnitude of the current drawn by the occupancy detector circuit 232is approximately equal to the magnitude of the total current drawn bythe other circuitry of the occupancy sensor 120. For example, themagnitude of the average current drawn from each of the batteries V1, V2is less than approximately 7 μA. The controller 230 is operable tomonitor the magnitude of the first battery voltage V_(CC1) of the firstbattery V1 and to transmit a digital message representative of alow-battery condition to the dimmer switch 110 when the magnitude of thefirst battery voltage V_(CC1) drops below a predetermined level. Inresponse to receiving the low-battery digital message, the dimmer switch110 may, for example, blink one or more of the visual indicators 118 toindicate that the batteries V1, V2 are low. Since magnitudes of thecurrents drawn from the batteries V1, V2 are approximately the same, thedimmer switch 110 assumes that the magnitudes of the first and secondbattery voltages V_(CC1), V_(CC2) are decreasing in a similar fashion.

FIG. 3 is a simplified circuit diagram of the occupancy detector circuit232. The occupancy detector circuit 232 includes the PIR detector 310,which may comprise, for example, part number LHi1128 manufactured byPerkinElmer, Inc. The PIR detector 310 receives power from the secondbattery V2 via a low-pass filter comprising a resistor R312 and acapacitor C314, which operate to minimize the noise introduced to theoccupancy detector circuit 232 from the second battery V2. For example,the resistor R312 may have a resistance of 22Ω, and the capacitor C314may have a capacitance of 0.01 μF. The PIR detector 310 generates anoutput signal characterized by a low frequency (e.g., approximately 0.3Hz to 8 Hz) and representative of the change in infrared energy detectedby the PIR detector 310. These changes in infrared energy are typicallyrepresentative of the occupant moving in the space.

The output of the PIR detector 310 is pulled down towards the secondcircuit common by a resistor R315 (e.g., having a resistance of 1 MΩ)and is coupled to a four-stage amplifier circuit via a capacitor C316(e.g., having a capacitance of 1 μF) and a resistor R318 (e.g., having aresistance of 10 kΩ). The first stage of the amplifier circuit comprisesan operational amplifier (OP amp) U320 and has a gain of approximately70. A non-inverting input of the OP amp U320 is coupled to the secondcircuit common via a capacitor C322 (e.g., having a capacitance of 0.01μF). Two resistors R324, R325 are connected in series between the secondbattery voltage V_(CC2) and the second circuit common and both have, forexample, resistances of 1 MΩ. The non-inverting input of the OP amp U320is coupled to the junction of the resistors R324, R325 via a resistorR326 (e.g., having a resistance of 1 MΩ). The series-combination of aresistor R328 (e.g., having a resistance of 14.3 kΩ) and a capacitorC330 (e.g., having a capacitance of 100 μF) is coupled between theinverting input of the OP amp U320 and the second circuit common. Acapacitor C332 is coupled in parallel with the capacitor C330 and has,for example, a capacitance of 0.1 μF. The parallel-combination of aresistor R334 and a capacitor C335 is coupled between the invertinginput and the output of the OP amp U320.

The output of the OP amp U320 is coupled to the non-inverting input of asecond OP amp U336 via two resistors R338, R340 (e.g., havingresistances of 118 kΩ and 845 kΩ, respectively). The inverting input ofthe second OP amp U336 is coupled to the output of the OP amp, such thatthe second OP amp operates as a buffer (i.e., forming the second stageof the amplifier circuit). The non-inverting input is coupled to thesecond circuit common through a capacitor C342 (e.g., having acapacitance of 0.01 μF). The junction of the two resistors R338, R340 iscoupled to the output of the OP amp U336 via a capacitor C344 (e.g.,having a capacitance of 0.047 μF).

The third and fourth stages of the amplifier circuit of the occupancydetector circuit 232 are similar to the first and second stages,respectively. The third stage comprises a third OP amp U320′ and alsohas a gain of approximately 70. The output of the second OP amp U336 isconnected to the non-inverting input of the third OP amp U320′ via aresistor R346 (e.g., having a resistance of 1 MΩ).

The fourth stage comprises a fourth OP amp U336′, which also operates asa buffer. Thus, the total gain of the occupancy detector circuit 232 isapproximately 4900. The output of the fourth OP amp U336′ is used togenerate the occupancy control signal V_(OCC), which is provided to anoccupancy control signal input (e.g., an analog input) of the controller230. Two resistors R350, R352 are connected in series between the secondbattery voltage V_(CC2) and the second circuit common and both have, forexample, resistances of 1 MΩ. A capacitor C354 is coupled between theoutput of the fourth OP amp U320′ and the junction of the two resistorsR350, R352, and has, for example, a capacitance of 1 μF. A resistor R356is coupled between the junction of the two resistors R350, R352 and theoccupancy control signal input of the controller 230 and has, forexample, a resistance of 1 MΩ. The occupancy control signal input of thecontroller 230 is coupled to the second circuit common through acapacitor C358 (e.g., having a capacitance of 0.01 μF). The controller230 converts the occupancy control signal V_(OCC) to a digital signalusing, for example, an internal analog-to-digital converter (ADC). Aspreviously mentioned, the occupancy detector circuit 232 draws a currenthaving a magnitude of approximately 7 μA or less from the second batteryV2.

FIG. 4A is a front exploded perspective view and FIG. 4B is a rearexploded perspective view of one of the occupancy sensors 120. Theoccupancy sensor 120 comprises a base portion 412 and a flat, circularmounting plate 450 (i.e., a bottom plate), which is releasably attachedto the base portion. The enclosure 122 comprises an integral cylindricalwall 415 extending from the periphery of the front surface 125, suchthat the wall forms a shallow, plastic cup and defines a generally, flatdisk-shaped volume. The mounting plate 450 is disposed in a planeparallel to the plate of the front surface 125 of the enclosure 122 andhas a diameter less than the diameter of the front surface. The frontsurface 125 of the enclosure 122 has a diameter greater than about 3inches and the occupancy sensor 120 has a height from the front surfaceto the mounting plate 450 of less than about 1.5 inches.

The circuitry of the occupancy sensor 120 is mounted to a printedcircuit board (PCB) 410, which is connected to the base portion 412. Thebase portion 412 is adapted to be connected to the housing 122 via aplurality of tabs 414 received by snaps 416 of the base portion. The PIRdetector 310 is mounted to the center of the PCB 410 and is aligned withthe lens 124. When the base portion 412 is coupled to the housing 122,the lens 124 is operable to direct the infrared energy from the spacetowards the PIR detector 310.

The occupancy sensor 120 further comprises a multi-functional structure420, which is located between the housing 122 and base portion 412. FIG.4C is a perspective view of the multi-functional structure 420. Themulti-functional structure 420 comprises actuation posts 422, 424, 426,which protrude through openings 428 in the front surface 125 of theoccupancy sensor 120 to allow for actuation of tactile switches 430 onthe PCB 410 from the front surface. The actuation posts 422, 424, 426comprise a portion of the plurality of actuators 236 of the occupancysensor 120 and are used during configuration of the lighting controlsystem 100 to verify the operation of the occupancy sensor and thelighting control system. The multi-functional structure 420 alsocomprises a light pipe 432 positioned parallel to the third actuationpost 426 for conducting light from one of the visual indicators 238(i.e., one of the LEDs) mounted on the PCB 410 to the front surface 125of the occupancy sensor 120.

The batteries V1, V2 are housed in battery compartments 434 of the baseportion 412. FIG. 4D is a rear perspective view of the base portion withthe batteries V1, V2 removed. When installed in the battery compartments434, the batteries V1, V2 are electrically connected to the circuitry ofthe occupancy sensor 120 via electrical contacts 436 and are supportedby battery supports 438 of the multi-functional structure 420. Themulti-functional structure 420 further comprises battery-removal tabs440 that aid in removing the batteries V1, V2 from the batterycompartments 434. When the tabs 440 are pulled away from the baseportion 412, flexible arms 442 of the multi-functional structure 420flex, such that the battery supports 438 force the batteries V1, V2 outof the battery compartments 434.

As shown in FIGS. 4A and 4B, the mounting plate 450 forms a circulardisk and allows the occupancy sensor 120 to be mounted to a ceiling orwall. The mounting plate 450 is first attached to the ceiling or wallvia screws (not shown) received through attachment openings 452 of themounting plate 450 and into anchors (not shown) in the ceiling or wall.The base portion 412 (along with the housing 122) is then rotatedclockwise around the perimeter of the mounting plate 450, such thatflanges 454 of the base portion 412 are received by attachment slots 456of the support plate. The mounting plate 450 permits the mounting of theoccupancy sensor 120 to selected positions within the space to produceoptimal operation of the occupancy sensor.

The remainder of the plurality of actuators 236 of the occupancy sensor120 are provided on the rear surface of the base portion 412 (as shownin FIGS. 4B and 4D) and comprise an assign button 460, an unassignbutton 462, an occupancy detection criteria (ODC) button 464, an ambientlight threshold (ALT) button 466, and an occupancy sensor timeout period(OSTP) button 468. Each of the buttons 460, 462, 464, 466, 468 is formedas an integral part of the base portion 412 and comprises an actuationknob at the end of a flexible arm provided in an elongated U-shapedslot. The actuation knob of each button 460, 462, 464, 466, 468 may bedepressed, thus flexing the flexible arm of the button, such that theactuation knob actuates a tactile switch (not shown) mounted to thebottom side of the PCB 410.

During configuration of the lighting control system 100, the user maysimultaneously press and hold the toggle button 114 of the dimmer switch110 and the assign button 460 of one of the occupancy sensors 120 tolink the dimmer switch and the one of the occupancy sensors. The usermay also simultaneously press and hold the toggle button 114 of thedimmer switch 110 and the unassign button 462 of the occupancy sensor120 to unassign the occupancy sensor from the dimmer switch. Thelighting control system 100 may comprise a plurality of occupancysensors 120 that may all be assigned to one dimmer switch 110, such thatthe dimmer switch is responsive to each of the occupancy sensors. Theuser simply needs to repeat the assignment procedure for each of theplurality of occupancy sensors 120.

The occupancy detection criteria button 464, the ambient light thresholdbutton 466, and the occupancy sensor timeout period button 468 allow foradjustment of various characteristics of the occupancy sensor 120.Consecutive actuations of the occupancy detection criteria button 464cause the controller 230 to adjust an occupancy detection criteria, usedto determine whether the space is occupied, between a number of values,i.e., settings (e.g., three values). For example, actuations of theoccupancy detection criteria button 464 may cause the controller 230 toadjust the predetermined occupancy voltage threshold to which themagnitude of the occupancy control signal V_(OCC) is compared between aminimum value, a middle value, and a maximum value. Alternatively,actuations of the occupancy detection criteria button 464 may cause thecontroller 230 to adjust a gain applied to the occupancy control signalV_(OCC) before the magnitude of the occupancy control signal V_(OCC) iscompared to the occupancy voltage threshold. Similarly, the ambientlight threshold button 466 and the occupancy sensor timeout periodbutton 468 allow the user to adjust the values of the ambient lightthreshold and the occupancy sensor timeout period T_(TIMEOUT),respectively. A portion of the visual indicators 238 are mounted to thebottom side of the PCB 410 and shine through openings 470 in the baseportion 412. The visual indicators 238 mounted to the bottom side of thePCB 410 are illuminated by the controller 230 to distinguish which ofthe values of the occupancy detection criteria, the ambient lightthreshold and the occupancy sensor timeout period T_(TIMEOUT) areselected.

FIG. 5 is a flowchart of a rear actuator procedure 500 executed by thecontroller 230 of each occupancy sensor 120 when one of the actuators460, 462, 464, 466, 486 on the rear surface of the base portion 412 ispressed at step 510. First, the serial number of the occupancy sensor120 is retrieved from the memory 240 at step 512, such that the serialnumber can be transmitted in a digital message to the dimmer switch 110.If the assign button 460 is pressed at step 514, an assign message(including the serial number) is transmitted to the dimmer switch 110 atstep 516 and the rear actuator procedure 500 exits. Similarly, if theunassign button 462 is pressed at step 518, an unassign message(including the serial number) is transmitted to the dimmer switch 110 atstep 520, before the rear actuator procedure 500 exits.

If neither the assign button 460 nor the unassign button 462 is beingpressed at steps 514 and 518, the controller 230 determines whether theoccupancy detection criteria button 464, the ambient light thresholdbutton 466, or the occupancy sensor timeout period button 468 is beingpressed. Specifically, if the occupancy detection criteria button 464 ispressed at step 522, the controller 230 selects the next of the threeselectable values for the occupancy detection criteria at step 524. Atstep 526, the controller 230 illuminates the next of the three visualindicators 238 (that are linearly arranged next to the occupancydetection criteria button 464 as shown in FIG. 4D). The controller 230then stores the new value of the occupancy detection criteria in thememory 240 at step 528. If the ambient light threshold button 466 ispressed at step 530, the controller 230 selects the next value for theambient light threshold at step 532, illuminates the next of the visualindicators 238 at step 534, and stores the new ambient light thresholdvalue in the memory 240 at step 536. If the occupancy sensor timeoutperiod button 468 is pressed at step 538, the controller 230 selects thenext value for the occupancy sensor timeout period T_(TIMEOUT) at step540, illuminates the next of the visual indicators 238 at step 542, andstores the new value of the occupancy sensor timeout period T_(TIMEOUT)in the memory 240 at step 544.

FIGS. 6A and 6B are simplified flowcharts of a dimmer actuator procedure600 executed by the controller 214 of the dimmer switch 110 in responseto an actuation of the toggle actuator 114 or the intensity adjustmentactuator 116 at step 610. If the toggle actuator 114 is actuated at step612, the controller 214 initializes a button timer to zero seconds andstarts the button timer increasing with respect to time at step 614. Thebutton timer is used to determine how long the toggle actuator 114 ispressed. If the toggle actuator 114 is still being pressed at step 616,a determination is made as to whether the button timer is less than apredetermined button hold time, e.g., five (5) seconds, at step 618. Thedimmer actuator procedure 600 loops until either the toggle actuator 114is released at step 616 or the button timer has exceeded thepredetermined button hold time at step 618. If the toggle button 114 isstill pressed at step 616 and the button timer is greater than thepredetermined button hold time at step 618, the controller 214 executesan assignment procedure 700, which will be described in greater detailbelow with reference to FIG. 7.

During the assignment procedure 700, the dimmer switch 110 may beassigned to one or more occupancy sensors 120. Specifically, thecontroller 214 is operable to store the serial numbers of the assignedoccupancy sensors 120 in the memory 216. Thereafter, the controller 214is responsive to digital messages received from the assigned occupancysensors 120. If the dimmer switch 110 is assigned to at least oneoccupancy sensor 120, the controller 214 starts the failsafe timerwhenever the lighting load 104 is toggled from off to on.

Referring back to FIG. 6A, if the toggle actuator 114 is released atstep 616 while the button timer is less than the predetermined buttonhold time at step 618, the controller 214 controls the lighting load 104appropriately. Specifically, if the lighting load 104 is on at step 620,the controller 214 turns the lighting load off at step 622 and stops thefailsafe timer at step 624, before the dimmer actuator procedure 600exits. If the lighting load 104 is off at step 620, the controller 214turns the lighting load on at step 625. If there is a serial number ofone of the occupancy sensors 120 stored in the memory 216 at step 626,the controller 214 starts the failsafe timer at step 628 and the dimmeractuator procedure 600 exits.

Referring to FIG. 6B, if the toggle actuator 114 is not pressed at step612, but the upper portion 116A of the intensity adjustment actuator 116is pressed at step 630, a determination is made as to whether thelighting load 104 is off at step 632. If the lighting load 104 is off atstep 632, the controller 214 turns the lighting load on to the minimumintensity at step 634. If there is a serial number of an occupancysensor 120 stored in the memory 216 at step 636, the controller 214starts the failsafe timer at step 638 and the dimmer actuator procedure600 exits. If the lighting load 104 is on at step 632 and the dimmerswitch 110 is not at the maximum intensity at step 640, the controller214 increases the lighting intensity of the lighting load 104 by apredetermined increment at step 642. If the dimmer switch 110 is at themaximum intensity at step 640, the controller 214 does not adjust thelighting intensity. If there is a serial number of an occupancy sensor120 stored in the memory 216 at step 644, the controller 214 restartsthe failsafe timer at step 646 and the dimmer actuator procedure 600exits.

If the lower portion 116B of the intensity adjustment actuator 116 ispressed at step 648 and the lighting load 104 is off at step 650, thedimmer actuator procedure 600 exits. If the lighting load 104 is on atstep 650 and the dimmer switch 110 is not at the minimum intensity atstep 652, the controller 214 decreases the lighting intensity by apredetermined increment at step 654. If the dimmer switch 110 is at theminimum intensity at step 652, the controller 214 does not turn off thelighting load 104. If there is a serial number of an occupancy sensor120 stored in the memory 216 at step 644, the controller 214 restartsthe failsafe timer at step 646 and the dimmer actuator procedure 600exits.

FIG. 7 is a simplified flowchart of the assignment procedure 700executed by the controller 214 of the dimmer switch 110 if the toggleactuator 114 is pressed and held for greater than the predeterminedbutton hold time at step 618 of the dimmer actuator procedure 600. Theassignment procedure 700 is executed as long at the toggle actuator 114is held. At step 712, the controller 214 first begins to cycle thevisual indicators 118, such that the visual indicators are consecutivelyturned on and off at a first rate. Next, the controller 214 determinesif an assign message or an unassign message has been received from anoccupancy sensor 120 at step 714. The assignment procedure 700 loopsuntil either the toggle actuator 114 is released at step 716 or eitheran assign message or an unassign message is received at step 714. If thetoggle actuator 114 is no longer being held at step 716, the controller214 stops cycling the visual indicators 118 at step 718 and theassignment procedure 700 exits.

When an assign message or an unassign message is received at step 714while the toggle actuator 114 is still held, the controller 214 eitherstores the serial number of the received message in the memory 216 ordeletes the serial number from the memory. Specifically, if the receivedmessage is an assign message at step 720, and the serial number from thereceived message is not already stored in the memory 216 at step 722,the controller 214 stores the serial number in the memory at step 724.The controller 214 then temporarily cycles the visual indicators 118 ata second rate (faster than the first rate) at step 726. The assignmentprocedure 700 then loops around such that another occupancy sensor 120may be assigned to the dimmer switch 110. If the received message is anunassign message at step 720, and the serial number from the receivedmessage is stored in the memory 216 at step 728, the controller 214deletes the serial number from the memory at step 730 and temporarilycycles the visual indicators 118 at the second rate at step 726.

FIG. 8 is a flowchart of an occupancy detection procedure 800 executedperiodically, e.g., every 50 msec, by the controller 230 of eachoccupancy sensor 120. As previously, the controller 230 uses theoccupancy timer to provide some delay in the adjustment of the state ofthe occupancy sensor. Whenever the controller 230 obtains a detectorreading that signifies an occupancy condition, the controllerinitializes the occupancy timer to the predetermined occupancy sensortimeout period T_(TIMEOUT) and starts the occupancy timer counting down.Therefore, the occupancy sensor 120 stays in the occupied state as longas the controller 230 receives indications of the occupancy conditionfrom the PIR detector before the occupancy timer expires. However, whenthe occupancy timer expires, the controller 230 changes to the vacantstate as will be described in greater detail below. The controller 230also uses a transmission timer (or “TX” timer) to keep track of when totransmit the next occupied-no-action command while in the occupiedstate.

Referring to FIG. 8, the controller 230 first reads the output of thePIR detector circuit 232 at step 810, for example, by sampling theoccupancy control signal V_(OCC). The controller 230 then determines ifthe detector reading signifies an occupancy condition in the space, forexample, by comparing the magnitude of the output voltage of the PIRdetector to the predetermined occupancy voltage threshold. If thedetector reading does not signify an occupancy condition in the space atstep 814, the occupancy detection procedure 800 simply exits. However,if the detector reading signifies an occupancy condition at step 814 andthe occupancy sensor 120 is presently in the vacant state at step 815,the controller 230 changes to the occupied state at step 816. At step818, the controller 230 initializes the occupancy timer to thepredetermined occupancy sensor timeout period T_(TIMEOUT) and starts theoccupancy timer (such that the occupancy timer decreases in value withtime). Then, the controller 230 reads the output of the ambient lightdetector 234 at step 820. If the value of the ambient light level isless than the predetermined ambient light level threshold at step 822,the controller 230 transmits (TX) the occupied-take-action command atstep 824. Otherwise, the controller 230 transmits the occupied-no-actioncommand at step 826. After transmitting either of the digital messagesat step 824 and 826, the controller 230 initializes and starts thetransmission timer counting down at step 828 before the occupancydetection procedure 800 exits.

When the occupancy detection procedure 800 is executed and the state ofthe occupancy sensor 120 is occupied at step 815, the controller 230simply initializes and starts the occupancy timer at step 830 before theoccupancy detection procedure 800 exits.

FIG. 9 is a flowchart of a transmission timer procedure 900 executed bythe controller 230 of each occupancy sensor 120 when the transmissiontimer expires at step 910 to allow the occupancy sensor to regularlytransmit the occupied-no-action commands to the dimmer switch 110. Ifthe occupancy sensor 120 is in the occupied state at step 912, thecontroller 230 transmits the occupied-no-action command to the dimmerswitch 110 at step 914 and restarts the transmission timer at step 916,before the transmission timer procedure 900 exits. If the occupancysensor 120 is in the vacant state at step 912 when the transmissiontimer expires at step 910, the controller 230 does not transmit anydigital messages and the transmission timer procedure 900 simply exits.

FIG. 10 is a flowchart of an occupancy timer procedure 1000 executed bythe controller 230 of each occupancy sensor 120 when the occupancy timerexpires at step 1010, i.e., when the occupancy sensor has determinedthat the space is unoccupied. Specifically, the controller 230 changesto the vacant state at step 1012 and transmits the vacant command to thedimmer switch 110 at step 1014 before the occupancy timer procedure 1000exits.

FIG. 11 is a simplified flowchart of a received message procedure 1100(or “RX” procedure) executed by the controller 214 of the dimmer switch110 in response to receiving a digital message from one of the occupancysensors 120 at step 1110. The controller 214 keeps track of the statesof the occupancy sensor 120 to which the dimmer switch 110 is assignedin response to the digital messages received from the occupancy sensors.Specifically, if the controller 214 receives an occupied-take-actioncommand or an occupied-no-action command from an occupancy sensor 120,the controller marks the serial number of the occupancy sensor as“occupied” in the memory 216. If the controller 214 receives a vacantmessage from the occupancy sensor 120, the controller marks the serialnumber of the occupancy sensor as “vacant” in the memory 216. Thecontroller waits for a vacant command from all of the occupancy sensorsto which the dimmer switch 110 is assigned before turning off thelighting load 104. However, if the failsafe timer expires, thecontroller 214 marks all of the serial numbers stored in the memory 216as vacant and turns the lighting load 104 off.

Referring to FIG. 11, after receiving the digital message at step 1110,the controller 214 first determines whether the serial number providedin the received digital message is stored in the memory 216 at step1112. If not, the controller 214 does not process the received digitalmessage and the received message procedure 1100 exits. If the serialnumber of the received digital message is stored in the memory 216 atstep 1112 and the received digital message is an occupied-take-actioncommand at step 1114, the controller 214 determines if any of the serialnumbers stored in the memory 216 are marked as occupied at step 1116 todetermine if the space is occupied or vacant. If there are no serialnumbers marked as occupied at step 1116 (i.e., the space has just becomeoccupied), the controller 214 controls the controllably conductivedevice 210 to turn on the lighting load 104 at step 1118 and starts thefailsafe timer at step 1120. The controller 214 then marks the serialnumber of the received digital message as occupied at step 1122 and thereceived message procedure 1100 exits. If there are serial numbersmarked as occupied at step 1116 (i.e., the space is occupied), thecontroller 214 marks the serial number of the received digital messageas occupied at step 1124. If the failsafe timer is presently on at step1126, the controller 214 restarts the failsafe timer at step 1128,before the received message procedure 1100 exits.

If the received digital message is an occupied-no-action command at step1130, the controller 214 does not adjust the amount of power deliveredto the lighting load 104. The controller 214 simply marks the serialnumber as occupied at step 1124 and restarts the failsafe timer at step1128 if the failsafe timer is on at step 1126. If the received digitalmessage is a vacant command at step 1132, the controller 214 marks theserial number as vacant at step 1134. If any of the serial numbers arestill marked as occupied at step 1136 (i.e., the space is stilloccupied), the controller 214 restarts the failsafe timer at step 1128if the failsafe timer is on at step 1126. However, if all of the serialnumbers are marked as vacant at step 1136 (i.e., the space is nowvacant), the controller 214 controls the lighting load 104 off at step1138 and stops the failsafe timer at step 1140, before the receivedmessage procedure 1100 exits.

FIG. 12 is a simplified flowchart of a failsafe timer procedure 1200executed by the controller 214 of the dimmer switch 110 when thefailsafe timer expires at step 1210. The controller 214 simply marks allof the serial numbers stored in the memory 216 as vacant at step 1212and turns off the lighting load 104 at step 1214 before the failsafetimer procedure 1200 exits.

According to a second embodiment of the present invention, the dimmerswitch 110 is operable to store in the memory 216 the values of thevarious operating characteristics of the lighting control system 100,e.g., the occupancy voltage threshold, the ambient light levelthreshold, and the occupancy sensor timeout period T_(TIMEOUT). Thedimmer switch 110 may provide, for example, an advanced programmingmode, such that the values of the operating characteristics may beadjusted in response to actuations of the toggle actuator 114 and theintensity adjustment actuator 116. An advanced programming mode isdescribed in greater detail in U.S. Pat. No. 7,190,125, issued Mar. 13,2007, entitled PROGRAMMABLE WALLBOX DIMMER, the entire disclosure ofwhich is hereby incorporated by reference. Since the user does not needto access the occupancy sensors 120 (which may be mounted to a ceiling)to adjust the operating characteristics, the use of the toggle actuator114 and the intensity adjustment actuator 116 of the dimmer switch 110allows for easier adjustment of the operating characteristics.

Because the dimmer switch 110 stores the values of the operatingcharacteristics, the occupancy sensors 120 must transmit multipledigital messages to the dimmer switch 110. For example, if the occupancyvoltage threshold can be programmed to three different levels, theoccupancy sensors 120 must determine occupancy in the space at all threedifferent levels and transmit the results of all three determinations tothe dimmer switch 110. The dimmer switch 110 is then able to use theresult of the detections that was determined at the occupancy voltagethreshold stored in the memory 216 to change between an occupied stateand a vacant state and to control the lighting load 104. The dimmerswitch 110 maintains an occupancy timer (or “occ” timer), such that thedimmer switch turns off the lighting load 104 after the occupancytimeout period T_(TIMEOUT).

FIG. 13 is a simplified flowchart of an occupancy detection procedure1300 executed periodically, e.g., every 50 msec, by the controller 230of each occupancy sensor 120 according to the second embodiment of thepresent invention. The controller 230 begins by sampling the output ofthe PIR detector circuit 232 at step 1310 and selecting the firstoccupancy voltage threshold at step 1312. If the sample is greater thanthe first occupancy voltage threshold at step 1314, the controller 230stores an occupancy detection for the first occupancy voltage thresholdin the memory 240 at step 1316. Otherwise, the controller 230 stores avacancy detection in the memory 240 at step 1318. If the controller 230has not determined occupancy at all of the possible values of theoccupancy voltage threshold at step 1320, the controller changes to thenext occupancy voltage threshold value at step 1322 and compares thereading from step 1310 to that occupancy voltage threshold at step 1314.When the controller 230 has determined occupancy for each of thepossible values of the occupancy voltage threshold at step 1320, theoccupancy detection procedure 1300 exits.

FIG. 14 is a simplified flowchart of a transmission procedure 1400executed periodically, e.g., every one minute, by the controller 230 ofeach occupancy sensor 120 according to the second embodiment of thepresent invention. First, the controller 230 retrieves the occupancy andvacancy detections from the memory 240 at step 1410. If there nooccupancy detections at step 1412 (i.e., there have not been anyoccupancy detections in the last minute), the transmission procedure1400 simply exits. Otherwise, the controller 230 selects the firstoccupancy voltage threshold at step 1414. If the occupancy sensor 120has determined at least one occupancy detection since the last executionof the transmission procedure 1400 (i.e., in the last minute) at step1416, the controller 230 transmits at step 1418 a digital message thatindicates an occupancy detection at the first occupancy voltagethreshold. If the occupancy sensor 120 did not determine at least oneoccupancy detection since the last execution of the transmissionprocedure 1400 at step 1416, the controller 230 transmits at step 1418 adigital message that indicates a Vacant detection at the first occupancyvoltage threshold.

If the controller 230 has not transmitted the results of the detectionsfor all of the possible occupancy voltage thresholds at step 1422, thecontroller selects the next occupancy voltage threshold at step 1424 anddetermines at step 1416 whether at least one occupancy detectionoccurred at that occupancy voltage threshold. The controller 230 theneither transmits an occupancy detection at step 1418 or a vacancydetection at step 1420 for the present occupancy voltage threshold. Whenthe controller 230 is finished transmitting all of the results of thedetections for the possible occupancy voltage thresholds at step 1422,the controller 230 reads the output of the ambient light detector 234 atstep 1426 and transmits the ambient light level reading to the dimmerswitch 110 at step 1428 before the transmission procedure 1400 exits.

FIG. 15 is a simplified flowchart of a received message procedure 1500executed by the controller 214 of the dimmer switch 110 in response toreceiving a digital message at step 1510. Specifically, the dimmerswitch 110 may receive a number of digital messages containing theresults of the detections at the various occupancy voltage thresholdsand the ambient light level reading. The controller 214 first determinesif the serial number of the received digital messages is stored in thememory 216 at step 1512. If not, the received message procedure 1500simply exits. However, if the serial number is assigned to the dimmerswitch 110 at step 1512, the controller 214 chooses at step 1514 to usethe result of the detection at the desired occupancy voltage threshold(i.e., as chosen by the user during configuration).

If the result of the detection from step 1514 is not an occupancydetection at step 1516, the received message procedure 1500 simplyexits. However, if the result of the detection is an occupancy detectionat step 1516, and the dimmer switch 110 is in the vacant state at step1518, the controller 214 changes to the occupied state at step 1520 andthen initializes and starts the occupancy timer at step 1522. If theambient light level (received in the digital messages at step 1510) isless than the ambient light level threshold stored in the memory 216 atstep 1524, the controller 214 turns on the lighting load 104 at step1526 and the received message procedure 1500 exits. If the ambient lightlevel is not less than the ambient light level threshold at step 1524,then the received message procedure 1500 exits.

If the result of the detection is an occupancy detection at step 1516and the dimmer switch 110 is in the occupied state at step 1518, thecontroller 214 restarts the occupancy timer at step 1528. If, at step1530, the result is the first occupancy detection for the occupancysensor 120 from which the digital messages were received at step 1512since the dimmer switch 110 was last in the vacant state, the controller214 determines whether the ambient light level is less than the ambientlight level threshold at step 1524 and may turn on the lighting load atstep 1526. Otherwise, the received message procedure 1500 simply exits.

FIG. 16 is a flowchart of an occupancy timer procedure 1600 executed bythe controller 214 of the dimmer switch 110 when the occupancy timerexpires at step 1610. Specifically, the controller 214 changes to thevacant state at step 1612 and turns off the lighting load 104 at step1614 before the occupancy timer procedure 1600 exits.

Alternatively, the controller 230 of the occupancy sensor 120 couldcompare the ambient light level reading to three different ambient lightlevel thresholds (e.g., high, medium, and low ambient light levelthresholds) and then transmit the results of the comparisons to thedimmer switch 110 in a manner similar to that described above withresponse to the PIR occupancy detection comparisons. The dimmer switch110 could then control the lighting load 104 based upon the resultantambient light level threshold comparison corresponding to the ambientlight level threshold stored in the memory 216.

FIG. 17A is a simplified block diagram of a lighting control system 100′having a dimmer switch 110′ according to a third embodiment of thepresent invention. The lighting control system 100′ may additionallycomprise one or more remote controls 130. The remote control 130comprises a plurality of actuators: an on button 132, an off button 134,a raise button 136, a lower button 138, and a preset button 140 (forrecalling a preset lighting intensity stored in the memory 216 of thedimmer switch 110′). Alternatively, the remote control 130 couldcomprises a plurality of preset buttons. The remote control 130transmits digital messages via the RF signals 106 to the dimmer switch110′ in response to actuations of any of the actuators. The dimmerswitch 110′ is responsive to digital messages containing the serialnumber of the remote control 130 to which the dimmer switch isassociated. The dimmer switch 110′ is operable to turn on and to turnoff the lighting load 104 in response to an actuation of the on button132 and the off button 136, respectively. The dimmer switch 110′ isoperable to control the lighting load 104 to the preset intensity inresponse to an actuation of the preset button 134.

During the setup procedure of the RF load control system 100′, thedimmer switch 110′ is associated with one or more remote controls 130. Auser simultaneously presses and holds the on button 132 on the remotecontrol 130 and the toggle button 114 on the dimmer switch 110′ to linkthe remote control 130 and the dimmer switch 110′. The user maysimultaneously press and hold the off button 136 on the remote control130 and the toggle button 114 on the dimmer switch 110′ to unassociatethe remote control 130 with the dimmer switch 110′. The configurationprocedure for associating the remote control 130 with the dimmer switch110′ is described in greater detail in co-pending commonly-assigned U.S.patent application Ser. No. 11/559,166, filed Nov. 13, 2006, entitledRADIO-FREQUENCY LIGHTING CONTROL SYSTEM, the entire disclosure of whichis hereby incorporated by reference.

FIG. 17B is a simplified state diagram illustrating how the dimmerswitch 110′ of the lighting control system 100′ controls the state ofthe lighting load 104 (i.e., between on and off). The dimmer switch 110′turns on the lighting load 104 when the first occupied-take-actioncommand is received from one of the occupancy sensors 120, when one ofthe dimmer actuator buttons (i.e., the toggle actuator 114 and theintensity adjustment actuator 116) is actuated to turn on the lightingload, or when digital messages are received from the remote control 130,i.e. when one of the remote control actuators (e.g., the on button 132,the raise button 136, or the preset button 140 of the remote control) isactuated to turn on the lighting load 104. Further, the dimmer switch110 turns off the lighting load 104 when the last vacant command isreceived from the occupancy sensors 120, when one of the dimmer actuatorbuttons is actuated to turn off the lighting load 104, when the failsafetimer expires, or when digital messages are received from the remotecontrol 130, i.e. when one of the remote control actuators (e.g., theoff button 134 of the remote control) is actuated to turn off thelighting load.

FIG. 17C is a simplified state diagram illustrating the state of thefailsafe timer of the dimmer switch 110′, which is similar to the statediagram of the failsafe timer as shown in FIG. 1C according to the firstembodiment of the present invention. However, the dimmer switch 110′ ofthe lighting control system 100′ additionally starts the failsafe timerwhen digital messages to turn on the lighting load 104 are received fromthe remote control 130 and at least one occupancy sensor 120 is assignedto the dimmer switch 110′. The dimmer switch 110′ restarts the failsafetimer when digital messages are received from any of the occupancysensors 120 or remote controls 130 to which the dimmer switch isassigned. The dimmer switch 110′ is also operable to stop the failsafetimer in response to receiving digital messages to turn off the lightingload 104 from the remote control 130.

FIG. 18 is a simplified schematic diagram of an occupancy detectorcircuit 232′ according to a fourth embodiment of the present invention.The occupancy detector circuit 232′ comprises a two-stage amplifiercircuit having two amplifier stages and no buffer stages. ResistorsR324′, R325′, R350′, R352′ have, for example, resistances of 1.5 MΩ. Theoccupancy detector circuit 232′ has a gain of approximately 4900 anddraws a current having a magnitude of approximately 5 μA or less fromthe second battery V2.

The present invention has been described with reference to the lightingcontrol system 100 having a plurality of occupancy sensors 120 (i.e.,the dimmer switch 100 is operable to both turn on and turn off thelighting load 104 in response to the occupancy sensors). However, theconcepts of the present invention can also be applied to a lightingcontrol system having a plurality of vacancy sensors in which the dimmerswitch 110 would not turn on, but would only turn off, the lighting load104 in response to the vacancy sensors. To implement this control withthe lighting control system described in the flowcharts of FIGS. 5-12,the dimmer switch 110 could simply not turn on the lighting load 104 andnot start the failsafe timer in response to receiving anoccupied-take-action command (i.e., skip steps 1118 and 1120 of thereceived message procedure 1100 of FIG. 11). Alternatively, the vacancysensors could simply transmit occupied-no-action commands rather thatthe occupied-take-action commands (at step 824 of the occupancydetection procedure 800 of FIG. 8). In both cases, the dimmer switch 100would only turn on the lighting load 100 in response to a manualactuation of the toggle actuator 114 or the intensity adjustmentactuator 116, using the dimmer actuator procedure 600 of FIGS. 6A and6B.

While the present invention has been described with reference to thedimmer switch 110 for controlling the intensity of the lighting load104, the concepts of the present invention could be applied to loadcontrol systems comprising other types of load control devices, such as,for example, fan-speed controls for fan motors, electronic dimmingballasts for fluorescent loads, and drivers for light-emitting diodes(LEDs). Further, the concepts of the present invention could be used tocontrol other types of electrical loads, such as, for example, fanmotors or motorized window treatments.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

What is claimed is:
 1. A load control device for controlling powerdelivered from an AC power source to an electrical load provided in aspace, the load control device comprising: a controllably conductivedevice adapted to be electrically coupled in series between the AC powersource and the electrical load to control the power delivered to theelectrical load; a wireless receiver configured to receive wirelesscontrol signals from at least two occupancy sensors, each of thewireless control signals received from the occupancy sensors comprisingone of an occupied wireless control signal indicating an occupancycondition in the space and a vacant wireless control signal indicating avacancy condition in the space, the vacant wireless control signal beinggenerated in response to occupancy in the space not being detected for atime period; a controller configured to control the controllablyconductive device to control the power delivered to the electrical loadin response to the wireless control signals received by the wirelessreceiver, the controller configured to determine whether an occupiedwireless control signal or a vacant wireless control signal has beenreceived from each of the occupancy sensors; and a memory configured tostore unique identifiers of each of the occupancy sensors, thecontroller configured to mark as occupied in the memory the uniqueidentifiers of the occupancy sensors from which occupied wirelesscontrol signals are received and to mark as vacant in the memory theunique identifiers of the occupancy sensors from which vacant wirelesscontrol signals are received; wherein the controller is configured toenable delivery of power to the electrical load when the uniqueidentifier for at least one of the occupancy sensors is marked asoccupied and cease the delivery of power to the electrical load when theunique identifiers of all of the occupancy sensors are marked as vacant,the controller storing in the memory the status of the unique identifierof each of the occupancy sensors as either occupied or vacant so thatthe controller does not disable the delivery of power to the electricalload in response to vacant wireless control signals received from theoccupancy sensors when at least one of the unique identifiers is markedas occupied.
 2. The load control device of claim 1, wherein thecontroller is configured to determine that no wireless control signalshave been received from at least one of the occupancy sensors for thelength of a predetermined timeout period.
 3. The load control device ofclaim 2, wherein the controller is configured to mark as vacant in thememory the unique identifier of the occupancy sensor from which nowireless control signals have been received for the length of thepredetermined timeout period.
 4. The load control device of claim 3,wherein the controller is configured to initialize a failsafe timer withthe predetermined timeout period in response to determining that nowireless control signals have been received from at least one of theoccupancy sensors, the controller configured to restart the failsafetimer in response to receiving wireless control signals from the atleast one occupancy sensor, the controller configured to mark as vacantin the memory the unique identifier of the at least one occupancy sensorwhen the failsafe timer expires.
 5. The load control device of claim 1,wherein the unique identifiers comprise unique serial numbers of therespective occupancy sensors.
 6. The load control device of claim 5,wherein each of the wireless control signals transmitted by theoccupancy sensors includes the unique serial number of the respectiveoccupancy sensor, the controller configured to be responsive to wirelesscontrol signals including the serial numbers that are stored in thememory.
 7. The load control device of claim 1, wherein, if theelectrical load is off, the controller is configured to enable thedelivery of power to the electrical load in response to receiving anoccupied wireless control signal including an occupied-take-actioncommand.
 8. The load control device of claim 7, wherein, if theelectrical load is off, the controller is configured to maintain theelectrical load off in response to receiving an occupied wirelesscontrol signal including an occupied-no-action command.
 9. The loadcontrol device of claim 1, wherein the electrical load is a lightingload and the load control device is a dimmer.
 10. The load controldevice of claim 1, wherein the wireless receiver is configured toreceive an actuator wireless control signal from a remote control, theremote control configured to transmit the actuator wireless controlsignal in response to an actuation of an actuator of the remote control,the controller configured to enable the delivery of power to theelectrical load in response to receiving the actuator wireless controlsignal from the remote control.
 11. A load control system forcontrolling power delivered from an AC power source to an electricalload provided in a space, the load control system comprising: at leasttwo occupancy sensors, each occupancy sensor configured to independentlydetect an occupancy condition in the space and to transmit an occupiedwireless control signal to the load control device in response todetecting an occupancy condition in the space, the occupancy sensorsfurther configured to transmit a vacant wireless control signal to theload control device in response to detecting a vacancy condition in thespace, the vacant wireless control signal being generated in response tooccupancy in the space not being detected for a time period; and a loadcontrol device adapted to be electrically coupled in series between theAC power source and the electrical load to control the amount of powerdelivered to the electrical load, the load control device configured toreceive the occupied and vacant wireless control signals from theoccupancy sensors, the load control device configured to determinewhether an occupied wireless control signal or a vacant wireless controlsignal has been received from each of the occupancy sensors, the loadcontrol device configured to store in a memory a unique identifier ofeach of the occupancy sensors, the load control device configured tomark as occupied the unique identifiers of the occupancy sensors fromwhich occupied wireless control signals are received and to mark asvacant the unique identifiers of the occupancy sensors from which vacantwireless control signals are received; wherein the load control deviceis configured to enable delivery of power to the electrical load whenthe unique identifier for at least one of the occupancy sensors ismarked as occupied and cease the delivery of power to the electricalload when the unique identifiers of all of the occupancy sensors aremarked as vacant, the load control device storing in the memory thestatus of the unique identifier of each of the occupancy sensors aseither occupied or vacant so that the load control device does notdisable the delivery of power to the electrical load in response tovacant wireless control signals received from the occupancy sensors whenat least one of the unique identifiers is marked as occupied.
 12. Theload control system of claim 11, wherein the load control device isconfigured to determine that no wireless control signals have beenreceived from at least one of the occupancy sensors for the length of apredetermined timeout period.
 13. The load control system of claim 12,wherein the load control device is configured to mark as vacant theunique identifier of the occupancy sensor from which no wireless controlsignals have been received for the length of the predetermined timeoutperiod.
 14. The load control system of claim 13, wherein the loadcontrol device is configured to initialize a failsafe timer with thepredetermined timeout period in response to determining that no wirelesscontrol signals have been received from at least one of the occupancysensors, the load control device configured to restart the failsafetimer in response to receiving wireless control signals from the atleast one occupancy sensor, the load control device configured to markas vacant the unique identifier of the at least one occupancy sensorwhen the failsafe timer expires.
 15. The load control system of claim11, wherein the unique identifiers comprise unique serial numbers of therespective occupancy sensors.
 16. The load control system of claim 15,wherein each of the wireless control signals transmitted by theoccupancy sensors includes the unique serial number of the respectiveoccupancy sensor, the load control device configured to be responsive towireless control signals including the stored serial numbers.
 17. Theload control system of claim 11, wherein, if the electrical load is off,the load control device is configured to enable the delivery of power tothe electrical load in response to receiving an occupied wirelesscontrol signal including an occupied-take-action command.
 18. The loadcontrol system of claim 17, wherein, if the electrical load is off, thecontroller is configured to maintain the electrical load off in responseto the wireless receiver receiving an occupied wireless control signalincluding an occupied-no-action command.
 19. The load control system ofclaim 11, wherein the electrical load is a lighting load and the loadcontrol device is a dimmer.
 20. The load control system of claim 11,further comprising: a remote control comprising an actuator andconfigured to transmit an actuator wireless control signal to the loadcontrol device in response to an actuation of the actuator; wherein theload control device is configured to enable the delivery of power to theelectrical load in response to receiving the actuator wireless controlsignal from the remote control.